Financial Guarantee Insurance Contracts - Summary of Loss Reserve Roll-Forward, Net of Subrogation Recoverable and Reinsurance (Detail) € in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2016 EUR (€)	Dec. 31, 2015 USD ($)	Dec. 31, 2015 EUR (€)	Dec. 31, 2014 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Less reinsurance on loss and loss expense reserves	$ 44,059
Prior years:
Add reinsurance on loss and loss expense reserves	30,767		$ 44,059
Balance Of Rmbs Subrogation Recoveries Net Of Reinsurance						$ (1,878,740)	$ (2,800,149)
Successor [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Exchange	(77,578)		(24,831)		$ (36,587)
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	(11,489)		(768,707)		(545,574)
Ceded Loss And Loss Expenses Paid Not Yet Recovered						(349)	(60)	$ (517)
Schedule Of Insured Financial Obligations With Credit Deterioration Reductions Of Gross Claim Liability Rmbs Subrogation						1,907,035	2,829,575	2,523,540	$ 2,206,598
Policyholder Benefits and Claims Incurred, Ceded	(5,421)		(47,085)		(21,164)
Net Incurred RMBS Subrogation Recoveries	71,369		303,633		481,669
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning gross loss and loss expense reserves	2,858,813		3,798,733		5,470,234
Less reinsurance on loss and loss expense reserves	44,059		100,355		122,357
Beginning balance of net loss and loss expense reserves	2,814,754		3,698,378		5,347,877
Current year:
Claim and loss expense payments, net of subrogation and reinsurance	(5,371)		0		(17)
Prior years:
Claim and loss expense (payments) recoveries, net of subrogation and reinsurance	944,955		(90,086)		(1,067,321)
Liability for Unpaid Claims and Claims Adjustment Expense, Net	2,814,754		3,698,378		5,347,877	$ 3,665,271	$ 2,814,754	$ 3,698,378	$ 5,347,877
Add reinsurance on loss and loss expense reserves	30,767		44,059		100,355
Ending gross loss and loss expense reserves	3,696,038		2,858,813		3,798,733
Current Year Claims and Claims Adjustment Expense	6,675		1,183		309
Prior Year Claims and Claims Adjustment Expense	(18,164)		(769,890)		(545,883)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	(939,584)		90,086		1,067,338
Euro Member Countries, Euro
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning gross loss and loss expense reserves	19,019	€ 17,515	16,094	€ 13,300
Prior years:
Ending gross loss and loss expense reserves	$ 21,375	€ 20,297	$ 19,019	€ 17,515	$ 16,094